1. Field of the Invention
This invention relates to an ink-jet head and more particularly to a low-cost ink-jet head which facilitates connection of driving electrodes ink-ink channels to external wirings and formation of a common ink chamber, which is compact and easy to produce, which generates little heat, and which is driven-by high frequencies.
2. Description of the Related Art
A conventional well-known ink-jet head is a shear-mode ink-jet head which emits ink from a channel which is cut in a piezo-electric substrate through a nozzle by applying a voltage to the electrodes of driving walls which partition channels and shear-deforming the driving walls. This ink-jet head uses a so-called harmonica-shaped head chip which comprises driving walls made of piezo-electric elements, channels partitioned by the driving walls, ink inlets placed in the front side of the channels, and ink outlets placed in the rear side of the channels. In this configuration of the harmonica-shaped head chip, the ink outlet, the channel, and the inlet are disposed approximately in a straight line. This configuration can increase the yield of head chips from a single wafer and the productivity of head chips.
In such an ink-jet head structure, the size and shape of the channel are approximately fixed between the inlet and the outlet. This is called a straight type channel. Further, the head chip must have electrodes provided outside the chip to supply a voltage to the driving electrodes of each driving wall from the electrodes on the FPC (flexible printed circuit).
There have been some technologies to provide such electrodes outside a head chip. Japanese Non-Examined Patent Publication H10-217456 discloses a technology of extending a wire which is connected to a driving electrode of each channel from the front side of the channel to the top or bottom surface of a head chip and connecting the wire to a driving circuit.
Japanese Non-Examined Patent Publication 2002-283560 discloses a technology of laminating a non-piezo-electric member on a piezo-electric element member having a channel groove, increasing the front and rear surfaces of the formed head chip with non-piezo-electric member, and forming an electrode to be electrically connected to the driving electrode on the surface (front or rear surface of the head chip) of the non-piezo-electric member.
Further, Japanese Non-Examined Patent Publication 2000-141653 discloses a technology of covering the all surfaces with a conductive layer and cutting thereof to isolate electrodes.
To extend the connecting electrode to the top or bottom surface of the head chip as disclosed in Japanese Non-Examined Patent Publication H10-217456, the wiring must pass through two surfaces (front or rear surface of the head chip and top or bottom surface of the head chip) from the driving electrode in each channel. Accordingly, two processes are required to form the connecting electrode: one for the front or rear surface of the head chip and the other for top or bottom surface of the head chip. This increases the man-hour and production cost of the print head. Further, the connecting electrode has a higher possibility of being damaged by sharp edges of the two surfaces.
Further, Japanese Non-Examined Patent Publication 2002-283560 provides non-piezo-electric members-to form connecting electrodes and widens the front and rear surfaces of the head chip. This increases the size of the head chip and goes against downsizing of the inkjet head. Worse still, it becomes harder to cut out head chips from laminated wafers since the laminated wafer is thicker than ever.
Further, the ink-jet head requires a common ink chamber for supplying ink to each channel. The common ink chamber must be so constructed to cover the channel inlets of channels in rows. This also increases the number of processes to produce the ink-jet head (a process of forming a connecting electrode which is electrically connectable to the FPC on the head chip and-a process of forming the common ink chamber). In other words, this makes the man-hour more complicated.